In one of Sweden’s most sensational murder cases, a 42-year-old woman has been charged with killing her father as well as her husband in two separate instances.

This 'sommarstugemordet' or 'summer cabin murder’, has gripped Sweden since the woman's father was stabbed to death and her mother was seriously wounded at their cottage on Lake Hjälmaren, Arboga last August.

In the indictment, the prosecution depicted the woman as a cold and manipulative person who had murdered her relatives for money.

"There's a lot that points to the main motive being money. It could also be jealousy or bad blood." prosecutor Johan Fahlander told Swedish news agency TT.

"She had living costs which were extremely high," added his colleague, Jessica Wenna. "She almost continually had higher expenses than her income, and was not able to live on her income without receiving help from her parents."

The woman denies carrying out the murders and her ex-boyfriend, who claims to be 19 years old but is believed by the prosecution to be 25, has admitted to stabbing the woman's mother and father.

Prosecutor Jessica Wenna said that she envisaged the 42-year-old "instructing and managing the 25-year-old" in the stabbings.

"The 42-year-old had a knife which she gave to the 25-year-old. He went into the house and stabbed the parents as they lay in bed. The 42-year-old's father died in his sleep. The mother was unconscious but later came to and dialed 112 [Sweden's emergency number]."

Police found the boyfriend's DNA under the father's fingernails and footprints that matched his shoes at the cabin.

But this is not the only murder the woman is being charged with. The prosecution believes that she also killed her husband and started planning the murders as far back as 2014.

In January 2015, she signed a life insurance policy for SEK 2 million in her then-husband's name. That August, he drowned and his body was later found next to the lake.

Only five days after, she tried make a claim on the policy. The insurance company found this suspicious as it usually takes much longer for relatives make such claims.

Despite the insurance company's suspicions, police initially ruled the death an accident, only reopening the case after the stabbings.

After exhuming the husband's body last November, police were able to prove that he had in fact been murdered.

"In court, we intend to present possible scenarios for how the murder took place," Wenna said.

In addition to being charged with two murders and one attempted murder, the woman has also been charged with fraud and threatening a public servant, after threatening two police officers during an interview.